Exploiting three dimensional vegetation structure to map wildland extent

Abstract Wildland and wilderness refer to areas of land which have been subject to little or no modification by human activity. These areas are important due to their role as wildlife habitats, the contributions they make to air and water quality and for human recreation. However, the intermingling of wildland and homes also increases the risk to life and property through wildfires. Management of this risk requires current and detailed knowledge of the spatial extent of wildland. What constitutes wildland vegetation is often difficult to define and may be influenced by both the horizontal continuity and vertical structure. We present a method to map wildland vegetation based on a combination of a vertically stratified cover threshold and spatial morphology. To test its practical application, the method was applied to airborne lidar data collected prior to a major wildfire that occurred in Australia in 2009. Distance between the lidar defined wildland extent and homes impacted by the fire was assessed and compared to previously published data using manual delineation of wildland extent. Results showed that the proportion of homes destroyed at the wildland boundary was greater than reported in previous fires and that there was an exponential decline in the proportion of homes destroyed as a function of distances to wildland. Although the method is objective the extent of wildland depends on the parameters which define thresholds of cover and lateral extent and connectivity. This highlights the need for a clear definition of wildland that can be used to determine extent using objective methods such as those described, whether this is in the context of quantifying wildfire vulnerability or other related applications such as ecological assessment and monitoring.